An improved colorimetric assay for T cell cytotoxicity in vitro

An improved colorimetric assay for estimation of cytotoxic T (Tc) cells is described. The method involves staining thioglycollate-induced macrophage targets with the dye neutral red prior to addition of cytotoxic T cells and estimating macrophage survival at the end of the assay by measuring dye remaining in viable targets. The method using macrophage targets is more sensitive than the 51Cr release assay employing macrophages or a variety of other targets. It may be used to detect alloreactive and H-2 restricted Tc cells in both short-term (4 h) and long-term (24 h) assays and overcomes some variability encountered with a previously described colorimetric procedure. Furthermore, the method is cheap, fast, reliable and avoids the use of radioactivity.